In an automobile, it is necessary that, at certain points, a wire harness extend between the exterior of the passenger compartment and the passenger compartment itself. Such harnesses are often splashed by water which can be transmitted into the passenger compartment. This causes corrosion of the mounting on the compartment side and also causes discomfort of the passengers and soiling of the mats and/or upholstery therein.
In order to deal with the foregoing problems, various waterproofing measures have been used to fix the wire harness on the wall in a watertight manner. In one such expedient, a sealant is infused in the gap between the wires and the inner surface of the grommet. Such a grommet is shown in FIGS. 7 and 8 hereof. Grommet G comprises a body which consists of enlarged diameter part 1 having receiving groove 1a and large opening 1b. Separator 5 fits into groove 1a to fix grommet G thereon. Enlarged part 1 blends into reduced diameter part 3 and is mounted on wire harness W with a gap between the internal surface of grommet G and the external surface of wire harness W. The gap is filled with sealant 3. For additional security, tape 4 is wrapped around the end of grommet G remote from large opening 1b.
The foregoing construction suffers from a number of disadvantages. Due to the large volume of expanded diameter part 1, a substantial amount of sealant 3 is necessary, thus increasing the cost of the assembly. Moreover, if curing of the sealant is started at an early stage, a danger exists that sealant 3 will set before it has an opportunity to flow into reduced diameter part 2. Therefore, assembly of grommet G places serious limitations on the stage at which curing can take place.
In an alternative prior art device as shown in FIG. 8, grommet G' is provided with reservoir 1c within large opening 1b which, in turn, is inside expanded diameter part 1. Wire harness W passes through part 1c to reduced diameter part 2 and sealant 3 flows from large opening 1b to reduced diameter part 2.
In order to apply grommets G and G' to wire harness W certain very specific steps are required. First, a bundle of wires is bound together with a tape or the like to form wire harness W. Thereafter, reduced diameter part 2 is expanded by a special jig to about 4 to 7 times its original diameter. In this condition, wire harness W is inserted into both reduced diameter part 2 and enlarged diameter part 1. Then, tape 4 is wound onto the end of reduced diameter part 2 remote from large opening 1b to fix the grommet thereon. Next the grommet is oriented so that large opening 1b faces up and sealant 3 is introduced into opening 1b or reservoir 1c. Finally, the sealant is cured.
Since the group of wires making up wire harness W extend for more than one meter on either side of the grommets, the appropriate orientation of the grommet and the subsequent introduction of the sealant are quite difficult. Moreover, in the case of grommet G' as shown in FIG. 8, expanded diameter part 1 surrounds the outer periphery of reservoir 1c and, therefore, interferes with the smooth movement of the nozzle injecting sealant 3 into the gap.
Furthermore, since it is essential that sealant 3 be introduced into the grommets after the application of tape 4, it then becomes necessary that the introduction of sealant 3 take place in the vicinity of the assembly line for harness W. This severely restricts the manufacturing operation, since it is impossible to introduce the sealant in a separate line or at a different location.
In addition to the foregoing, it has been customary to use two-liquid type sealants; such sealants cure very rapidly so that they must be introduced quickly into the grommets. It is necessary to bundle the wires, introduce them into the grommets, and wind the tape therearound before the sealant can be introduced. Since the introduction must take place at the assembly line, the operator carrying out this step can only work intermittently. This is an inefficient use of personnel. Furthermore, the necessary expansion of the diameter of the reduced diameter part (4 to 7 times) by the use of a jig necessitates additional labor and adds to the cost.